Tobacco use is the leading cause of preventable death in the U.S. Although the prevalence of smoking has declined to 17.8% among U.S. adults, 29.2% of those living in poverty report current smoking. Socioeconomic disadvantage is associated with a reduced likelihood of smoking cessation. There is mounting evidence that offering incentives for abstinence (i.e., Contingency Management [CM]) may be an effective approach for promoting short-term smoking cessation, though few studies have demonstrated longer-term effectiveness. In addition, little attention has been paid to socioeconomically disadvantaged smokers specifically in CM intervention studies. Our preliminary work indicates that offering small escalating financial incentives for smoking abstinence dramatically increases short-term cessation rates among socioeconomically disadvantaged smokers when incentives are included as an adjunct to standard clinic-based smoking cessation treatment. Additional work is needed to evaluate the influence of this CM approach in the longer- term with a rigorous and adequately powered trial. Thus, the aims of the proposed study are to: 1) evaluate the longer-term impact of an adjunctive, low-cost CM intervention (relative to usual care) on smoking abstinence rates among economically disadvantaged individuals participating in a clinic-based smoking cessation program, and 2) identify treatment mechanisms and contextual factors associated with cessation outcomes among intervention participants using both traditional and ecological momentary assessment approaches. Economically disadvantaged individuals participating in a clinic-based smoking cessation treatment (N = 320) will be randomly assigned to 1) usual care (UC; n = 160) or 2) UC plus financial incentives for biochemically- confirmed abstinence (CM; n = 160). Those randomized to the CM intervention will have the opportunity to earn small gift cards for biochemically-verified abstinence through 12 weeks post-quit. Specifically, participants may earn $20 for abstinence on the quit date, and this amount will increase by $5 with each successive abstinent visit through 4 weeks post-quit ($150 total). Participants may additionally earn $50 gift cards for abstinence at 8 and 12 weeks post-quit. Biochemically-verified 7-day point prevalence abstinence at 26 weeks post-quit (longer-term abstinence) will be the primary outcome variable, though smoking status will be assessed at all visits. We also hope to gain a better understanding of CM treatment mechanisms and to identify other factors that directly influence cessation via traditional questionnaire and smartphone-based ecological momentary assessment approaches. Smartphone technology allows for ?real-time? data collection to more accurately capture important cessation-related variables, and will be used to deliver gain-framed messagesto support and strengthen the CM intervention. Findings will provide insight about new treatment targets for intervention research, and will demonstrate an effective, inexpensive, and easily implementable means by which to improve longer-term smoking cessation rates among economically disadvantaged smokers.